Tungsten (W) is used as a gate material or a wire material for semiconductor products. However, tungsten at an unnecessary portion on a semiconductor substrate needs to be removed. Particularly, tungsten deposited on back side of a substrate or so-called bevel portion as a region in the range between an outer circumferential edge of the substrate and a few millimeters from the outer circumferential edge could cause contamination in subsequent processes or lead to unstable processes. Thus, it is desirable to completely remove tungsten at the unnecessary portion.
A chemical solution is dispensed to a bevel portion of a substrate while, for example, the substrate being rotated on a rotating stage. Tungsten deposited on the bevel portion is thereby etched by the chemical solution. A chemical solution containing hydrogen peroxide is known as an etchant of tungsten. From the viewpoint of improving productivity of a semiconductor device, the development of a chemical solution having a tungsten etching rate faster than that of the current chemical solution is desired.